After 45 mins of running i start to lose transmission and torque converter pressure, only leaks ive found are on top of transmission and the seal around the drive shaft goin into transmission, could this be problem? Transmission has lots of air in oil and didnt see any leaks around converter housing. Any help or ideas on what to check and look for would be great. Also with the pressure loss of course it wont move good its obviously slipping my temp gauge dont work on the converter. My next step is to check output flow on the charge pump im assuming thats the right direction? Thanks
late 70s case 450 dozer
- Thread starter jrobe44
- Start date
SLHawkins
Gold Member
- Joined
- Nov 23, 2007
- Messages
- 435
- Location
- Northern Virginia
- Tractor
- John Deere 5403, International Harvester 584
jrobe,
I have an old case 450 as well. What makes you say the transmission has a lot of air in the oil? Is it foamy? Also, what color the fluid? I need to check my manual, but I don't think these machines use the universal hydrualic/trans fluid. There are separate resevoirs for the hydrualics and transmission. Keep me posted on what you find out. I am still learning mine.
Hawk
I have an old case 450 as well. What makes you say the transmission has a lot of air in the oil? Is it foamy? Also, what color the fluid? I need to check my manual, but I don't think these machines use the universal hydrualic/trans fluid. There are separate resevoirs for the hydrualics and transmission. Keep me posted on what you find out. I am still learning mine.
Hawk
There is a charge pump located on the right side of ur motor that sucks oil from the transmission to somewhere around the torque converter?. Im not sure where or what its exactly called but was told if it suck air it could lose pressure/prime especially as oil temp rises and thins out. Im in the process of replacing hoses and leaks but wanted to know if the seal around the rear of the driveshaft could be the source of the problem. Yes oil is foamy and yellowish in color.
crazyal
Super Member
Do you have a pressure gauge for the charge pump? If so is the pressure dropping? On mine when you first start it there's a brief moment before the charge pump builds pressure. Once it does it's steady except for when you shift between forward and reverse. When it shifts the pressure drops and then quickly rebounds, less than a second. I've never looked but I think I would try changing the fluid and filter just to make sure you have the correct fluid in it that's in good shape.
I have a pressure gauge that says torque converter would that be hooked to the charge pump? If so mine does the same as yours with shifting and starting until after about 45 mins of run time then it starts to lose pressure and slip but i can let it idle for a minute or two and pat the accelerator and itll jump back up to normal pressure but it continues to lose when it gets hot. The transmission pressure gauge also loses pressure same as torque converter when it gets hot.
crazyal
Super Member
The way the system was taught to me is the charge pump feeds a valve inside the transmission. Inside the transmission are some clutch disks that are pressurized by the charge pump. I'm not sure if the gauge is measuring the pressure before or after that valve. If the pressure is not high enough the valve will not open, I would think that if the gauge is after the valve you'll see 0 pressure if the valve doesn't open. When the valve opens it sends fluid to the torque converter. I think I remember someone calling it a regulator valve. I would start off with replacing the fluid as it does go bad. If it's too thin it can leak internally in the charge pump and not allow enough pressure to build. Bad oil could also leak by seals in the TC and the clutch disks.
My charge pump went and I had to replace it. It's not a hard job, think it's right below the alternator. What was happening was when I would start it I would have no pressure at all unless I parked it with the front facing downhill. Once the pump made enough pressure it was fine. It did it cold or hot but I think it was worse when hot. It seamed like the charge pump had to suck the oil out of the tank.
My charge pump went and I had to replace it. It's not a hard job, think it's right below the alternator. What was happening was when I would start it I would have no pressure at all unless I parked it with the front facing downhill. Once the pump made enough pressure it was fine. It did it cold or hot but I think it was worse when hot. It seamed like the charge pump had to suck the oil out of the tank.
Thanks for the info it is greatly appreciated i jus gotta wait on my manuals to come in before i jump on it. Ive only had this dozer a week and only got to run it for an hr since ive had it. If not for bad luck i wouldnt have any 
SLHawkins
Gold Member
- Joined
- Nov 23, 2007
- Messages
- 435
- Location
- Northern Virginia
- Tractor
- John Deere 5403, International Harvester 584
Jrobe44,
I'd send pictures from the manual, but my scanner is down. The 450 has a transmission oil line suction screen (filter) located at the right, rear side of the engine. It is adjacent to the flywheel housing. There are 4 bolts that hold the screen head. In addition to the filter element, there are some o-rings that may need replacement.
There is also a oil filter on the pressure side. This filter is located inside the right-hand tank compartment in front of the hydraulic tank. You'll have to remove the right-hand tank side plate. This filter has a cover, back up ring, o-ring, retaining spring and relief valve.
The transmission oil filter breather cap is beneath the operator's seat adjacent to the transmission dipstick. Check and clean this too.
Hawk
I'd send pictures from the manual, but my scanner is down. The 450 has a transmission oil line suction screen (filter) located at the right, rear side of the engine. It is adjacent to the flywheel housing. There are 4 bolts that hold the screen head. In addition to the filter element, there are some o-rings that may need replacement.
There is also a oil filter on the pressure side. This filter is located inside the right-hand tank compartment in front of the hydraulic tank. You'll have to remove the right-hand tank side plate. This filter has a cover, back up ring, o-ring, retaining spring and relief valve.
The transmission oil filter breather cap is beneath the operator's seat adjacent to the transmission dipstick. Check and clean this too.
Hawk
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